Cisco IOS Software Releases 12.0 S

Changes in MBGP Commands Between 12.0S and 12.0T/12.1

Application Note

Changes in MBGP Commands Between 12.0S and 12.0T/12.1

MBGP support in the 12.0T branch of Cisco IOS® Software was introduced in version 12.0(6)T. Because of BGP enhancements in this release, this support came with new MBGP configuration commands.

Configuration Changes

Version 12.0T now uses an address family that separates the BGP unicast configuration from the BGP multicast configuration:

The following is RouterA's MBGP configuration with 12.0(8.1)S:


router bgp 5


no synchronization
network mask nlri unicast multicast
neighbor remote-as 5
neighbor remote-as 2 nlri unicast multicast
neighbor remote-as 5
neighbor remote-as 5
no auto-summary

Reload RouterA with 12.0(8.0.2)T and the configuration changes to the following:


router bgp 5


no synchronization
network mask
neighbor remote-as 5
neighbor remote-as 2
neighbor remote-as 5
neighbor remote-as 5
no auto-summary
address-family ipv4 multicast
neighbor activate
network mask

If there has been no previous MBGP configuration, you'll need to configure the address family manually. MBGP works correctly between a router configured with an address family (12.0T) and one using the nlri multicast (12.0S) configuration. MSDP configuration remains unaffected with 12.0T.

Address Family Options

These are the new Address Family Options:


RouterA(config)#router bgp 5
RouterA(config-router)#address-family ?



Address family
Address family


RouterA(config-router)#address-family ipv4 ?



  Address Family modifier
  Address Family modifier
  Specify parameters for a VPN Routing/Forwarding instance


Router Address Family configuration commands:



  Configure BGP aggregate entries
  BGP specific commands
  Set a command to its defaults
  Define an administrative distance
  Exit from Address Family configuration mode
  Description of the interactive help system
  Specify a neighbor router
  Specify a network to announce via BGP
  Negate a command or set its defaults

Address-family router submode usage information

To enter the address family submode for configuring routing protocols, such as BGP, RIP and static routing, use the address-family configuration command. To disable the address-family submode for configuring routing protocols, use the no form of this command.


Routing information for address family IPv4 is advertised by default when a BGP session is configured using the following command:
neighbor <ip address> remote-as <as number>

unless you execute the no bgp default ipv4-activate command.

Address-Family Usage Guidelines

Using the address-family command invokes the address family configuration submode:


RouterA(config)#router bgp 5
RouterA(config-router)# address-family ipv4 multicast

Within the address-family configuration submode, administrators can configure address-family-specific parameters for routing protocols, such as BGP, that can accommodate multiple Layer 3 address families.

To leave address family configuration submode and return to router configuration mode, type:



or simply:



You can find additional information about these new commands in the 12.0T and 12.1 Cisco IOS documentation.

Known Caveats

  • CSCdp28125 conversion from old BGP syntax to new is incomplete.

    Some BGP configuration information may be lost when converting from 12.0S to 12.0T/12.1. Peer group and router-reflector information may be affected. To work around this problem, re-enter peer group information under address-family ipv4multicast after upgrading.